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How to Calculate the Amount of Supplement for Feedings

Calculator and pencil on notebook.

You’ve seen it happen. The licensed healthcare professional tells the parents, “Oh, the baby isn’t gaining enough weight with breastfeeding. You need to offer some formula.” You find yourself wondering … how do I calculate the amount of supplement for each feeding?

Here’s the hard truth. To the best of my knowledge, there are no official recommendations or mandates to help you break down that daily quota into real-life measurements for each feeding.

There are plenty of unofficial recommendations out there, but that’s about it. And what I’m about to suggest isn’t official, either! But I’m hoping I can give you a few unofficial suggestions, some historically-accepted calculations, and a bunch of common sense. 

What factors determine the amount of daily amount supplement

Hopefully the medical professional who recommended the supplementation specified the number of ounces or milliliters for daily consumption based on an understanding of the baby’s needs and age.

What issues need to be solved, answered, or addressed? To me, it always boils down to three fundamental factors:

  • Needs: How much does the baby need to consume? That will be the basis by which we calculate the amount of supplement for the day.
  • Transfer: How much milk is the baby getting at breast?
  • Availability: The last question is how much milk the mother is producing.

In short, we can’t calculate the volume needed for each feeding unless we know the total daily amount of supplementation needed.

How can we determine the daily total of supplementation needed?

Let’s say for a minute that no specific number of ounces were stated by the person who is supervising the medical management of the baby. Or you question whether that number makes sense.

The answers — and I’m talking answers, plural — are elusive.

Fluid volume is one factor. Regardless of our age or our health status, we all need fluids. We cannot achieve optimal health with too little, or too much.  

Caloric and nutrient intake is another factor. Again, there’s no one answer. And the number of calories and nutrients a baby needs to grow at different ages and stages is likely to be a range, not an absolute number.

To add to the confusion about how to calculate the amount of supplement for the day or for each feeding, the “right” number is often calculated based on the needs of an exclusively formula-fed infant. That might not be “right” for the infant who is fed human milk

How can we calculate the amount of supplement at each feeding?

We can’t begin to calculate how much supplementation is needed unless we know the total amount of milk the baby needs each day.

But let me slow down for a moment.

I learned long ago, when talking to parents, that I need to specify the word “day.” When I say “per day” I don’t mean the daylight hours. I mean in a 24-hour period.

For a baby in the first few days

Often, we tend to think of “normal” as what formula-feeding babies consume. That’s not necessarily a good way to estimate how much a breastfed baby needs, especially in those few few days. The Academy of Breastfeeding Medicine and Kellams offer these guidelines for the first few days:

First 24 hours: 2-10 ml per feeding
24-48 hours: 5-15 ml per feeding
48-72 hours: 15-30 ml per feeding
72-96 hours: 30-60 ml per feeding.

Calculate the amount of daily supplement for and infant who weighs less than 10 pounds

The daily needs of a baby who weighs less than or equal to 10 pounds has historically been calculated as about 2-3 ounces per pound of body weight per day. Many people round that off to about 2.5 ounces per pound per day.

Again, I am not qualified to determine the needs of premature and/or compromised infants. But for full-term, healthy infants, here are some general guidelines.

So, starting with 6 pounds, here’s what you might consider:

This is very approximate, and a little flakey but it’s at least a starting point.

Most full-term healthy babies weigh 10 pounds or more by the end of the first month.

This calculation doesn’t work very well after the baby weighs about 10 pounds.

After the first month or so, healthy babies take in about 23-30 ounces per day, i.e., 680 ml to 887 ml. This has been shown in multiple studies (Cox et al, Neville et al, Allen et al.) years ago. Their conclusions are so strong that it’s unlikely any further studies would be funded to determine this.) And from my own casual observations, this feels about right to me.

Let’s say a 10-day-old baby takes in about 2.5 ounces of milk per feeding and has 10 feeding per day. That’s about 25 ounces per day.

However, after the baby is about 6 months old, and taking soft, semi-soft, or solid food, these guidelines might not apply at all.

Calculate amount of daily supplement for and infant after 6 months old

Two big factors affect milk intake after 6 months old. First, growth slows during the last half of the first year. And, babies are taking in soft, semi-soft, or solid foods after 6 months.  

Below is information from Diana West and Linda Pohl, IBCLC describing a combination of months and body weight. I’m no longer able to locate their original guidance, and I’ve modified the format below.

Again, to my knowledge there’s no scientific study to support this, but it makes a lot of sense to me.

Based on her idea, I’ve devised this table to help you calculate the amount of supplement for each feeding from the standpoint of age:

Using observation to determine satiation

Looks can be deceiving. But if you don’t look, you don’t stand a chance of getting any individualized guidance.

Here are some simple questions to ask yourself:

  • How much milk is the baby transferring at breast? To figure that out, test weigh the baby, before and after each feeding, using an electronic scale designed for that purpose. (Yes, there’s more to know about that.)
  • How much milk is being produced?  
  • How much weight is the baby gaining or losing over a few days? (It’s tough to say how often you should weigh the baby, it really depends on the circumstances.)

Here are a few considerations.

During the first 2 weeks, most term, healthy breastfed babies take in about 1.5 to 3 ounces (45 to 90 ml) at each feeding. (I’ve seen this hundreds of times.)

After 2 weeks, breastfed babies take in about 2-4 ounces (60-120 ml) at each feeding.

As you calculate the amount of supplement few “rules” to consider:

  • Consider offering about ½ ounce (15 ml) of formula supplementation after the baby breastfeeds. See if they take it.
  • If they still seem hungry, offer more. But remember, if they guzzle down several ounces, it can affect your milk supply. One episode like that might not make much difference but be prepared to find a way to continue regular breast stimulation in order to keep up supply.
  • Do not force or “coax” the baby into taking more than they want from the bottle.
  • If the baby gains more weight, offer less supplement.
  • If the baby gains less weight, offer more supplement.

Understand, these are very loosely-documented guidelines. Meaning, my message here is descriptive, not prescriptive; this is not medical advice. Each situation is different. All my suggestions apply to infants who are born at term and have no known compromising conditions. And all of this presumes that the family has sought medical help to rule out any underlying pathology.

My intention here is to relieve both the parent and the provider from the message of, “oh, just go home and give supplement,” and instead, to have a way to figure out what to do to make that happen.

A few other issues are related. This includes:

  • Recognizing babies that are underfed (Stay tuned for an upcoming post)
  • Making adjustments to supplementation amounts. (Stay tuned for an upcoming post)

How have you calculated the amount of supplement? What cues do you look for?

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  1. Jayne Voyles

    I would love to see something like this for the first three days, first week also. Often pediatricians start 12 hour old babies with 10-20 cc formula after every time at breast.

    PS: Thanks for all you are doing to advance the cause. You are a gift to the world of Lactation!

    • Marie Biancuzzo

      Ohhhhhhh, Jayne. Honestly, there are days when I wonder — what are they thinking? If they are not reading the research, could they just use some common sense? And how long will this keep happening? More than 40 years ago, this was happening and I thought — oh, some day it won’t. But here we are, decades later, and it’s still the same old story. I doubt that any of your physicians would care to hear what I have to say, but perhaps they will listen to the Academy of Breastfeeding Medicine. In their statement on supplementation they say 1st 24 hours; 2-10 ml per feeding; 24-48 hours 5-15 ml per feeding, 48-72 hours 15-30 ml per feeding, and 72-96 hours 30-60 ml per feeding. And you’re saying AFTER they take milk at the breast! I continue to be baffled. I admit, I’m a little worn out after all of these years. I’m flattered that you say I’m a gift, but honestly, sometimes I feel like just a tired old lady, squawking about the same stuff I was squawking about decades ago. I’m happy to pass the baton on to passionate, knowledgeable, energetic people like you, Jayne! Thank you for reading, and for helping me to keep on keeping on.

  2. Danielle

    So, I love this and appreciate this article and agree! However, my question is where is some evidenced based information with amounts that I can share with Pediatricians? For example, let’s just “hypothetically” say that a pediatrician tells a parent their 5 day old infant who has had more than a 10% weight loss needs to be eating more for weight gain. This parent is nursing their infant every 2-2.5 hours during the day and are waiting on a feeding evaluation from a lactation consultant. they are feeding their infant 1.5 ounces per feeding every two hours during night time feeds via pumping and expressed breast milk. The pediatrician tells them this is not enough because this baby was 9 pounds at birth and so he needs to “eat more” and she should be feeding him 3 ounces every 2 hours. How would you deal with this scenario, A ) with out undermining the pediatrician B) keeping on good terms with the pediatrician and discussing evidenced based amounts (for a 5 day old) with them so you weren’t just going in blind and telling them that is too much for a 5 day old. We all know they want to see the evidence and if they don’t, they won’t value what we have to say. I’m trying how to learn how to navigate lightly.

    • Marie Biancuzzo

      Danielle, you have articulated your question clearly, but my answer is very inadequate. First, you could try handing the pediatrician the ABM’s protocol on supplementation, which is unquestionably the most authoritative I know of. (And if there was something better, I would know!) But your real question isn’t about evidence, or about supplementation. Your real question is about cultural norms, physician power, and change theory. At least here in the US, breastfed infants are presumed to have the same needs and behaviors of formula-fed babies, which of course, they do not. (Plenty of “evidence” for that, but the evidence is simply ignored.) Second, we have medicalized the care of normal infants; physicians are thought to be in charge of a baby’s health, but oddly, they have little or no accurate information about breastfeeding during medical school. I’ve spent more than 40 years fighting this battle, and honestly, very little has changed during that time. I was fighting the fight for “evidence-based” care long before the term was coined (which was in the early 1990s). I felt sure that science and logic would prevail. I was wrong. Cultural attitudes, beliefs and values trump science and logic where it comes to breastfeeding. And, since I was “just a nurse” the physician’s word and opinion almost always trumped my solid, in-depth understanding of the existing literature. We continue to generate more evidence, and that’s great. But until we ALL become aware of, use, and value that information, little will change with the scenario you describe. (Which, by the way, is an exact description of what I was dealing with, more than 40 years ago. Your testimony shows how little progress we’ve made over the decades.) I was successful making headway with some doctors and some hospitals, but I was unsuccessful with others. Pick your battles. Count your wins when you get them. But recognize there’s no magic bullet for changing the underlying problem. Although things have gotten better, there’s a long road ahead.

  3. Jessica C Luginbuhl

    This is excellent!! Thank you for writing this. I’m just finishing up my year long IBCLC training at UNC Chapel Hill and I found this incredibly helpful.

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